Threaded Connection with Engaging Lugs for Electrical Submersible Pump

ABSTRACT

An electrical submersible pump assembly has modules including a pump, a motor, and a seal section. A threaded connection between at least two of the modules has a first adapter and a second adapter. A collar rotatably carried and axially movable on one of the adapters is in threaded engagement with threads of the other adapter when the threaded connection is made up. First adapter lugs are spaced circumferentially apart from each other around the first adapter. Second adapter slots are spaced circumferentially apart from each other around the second adapter. The lugs slide into the slots while the adapters are brought together. Each of the lugs and each of the slots have side edges that are parallel with the axis. The side edges of the lugs abut the side edges of the slots to prevent rotation of the first and second adapters relative to each other.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to provisional application Ser. No. 62/081,680, filed Nov. 19, 2014.

FIELD OF THE DISCLOSURE

This disclosure relates in general to electrical submersible pumps for wells and in particular to a threaded connection between modules of a pump assembly having lugs that mesh to prevent relative rotation between the modules, and in the case where the modules comprise tandem motors, to self-orient the mating electrical terminals.

BACKGROUND

Submersible well pump assemblies (ESP) are commonly used to pump well fluid from oil wells. A typical ESP includes a pump and an electrical motor. The pump may be a centrifugal motor having a large number of stages, each stage comprising an impeller and a diffuser. Alternately, the pump may be another type, such as a progressing cavity pump. An ESP includes a pressure equalizer that couples to the motor to reduce a pressure difference between dielectric lubricant in the motor and the hydrostatic pressure of the well fluid. The ESP may include other components, such as a gas separator and additional motors and pumps in tandem. The various components are normally brought to a well site in separate modules, then secured together.

Generally the modules of the ESP are connected together by bolts that secure mating flanges. In some wells, a vertical section leads around a bend to an inclined or horizontal section. Inserting a lengthy ESP around the bend can cause stresses to the bolts.

It has been proposed instead of bolted flanges to employ threaded collars that are rotated to secure the various modules of the ESP. An example of a threaded collar arrangement is shown in U.S. Pat. No. 6,557,905. The threaded collar fits around a neck of an adapter of one of the modules and engages threads on the adapter of the other module. Teeth on the rim of one of the adapters engage mating teeth on the other adapter to prevent rotation between the adapters.

If the modules being connected are tandem motors, electrical terminals in each adapter must be aligned and stabbed together. Alignment can be a problem during the connection process because the terminals are not readily visible as the adapters are brought together.

SUMMARY

An electrical submersible pump assembly has a plurality of modules including a pump, a motor, and a seal section for reducing a pressure differential between lubricant in the motor and hydrostatic pressure of well fluid. A threaded connection between at least two of the modules has a first adapter and a second adapter. The first and second adapters have a longitudinal axis. A collar is rotatably carried and axially movable on one of the adapters, the collar being in threaded engagement with threads of the other adapter when the threaded connection is made up. First adapter lugs are spaced circumferentially apart from each other around the first adapter. Second adapter slots are spaced circumferentially apart from each other around the second adapter. The lugs slide into the slots while the adapters are brought together. Each of the lugs and each of the slots have slide edges that are parallel with the axis. The side edges of the lugs abut the side edges of the slots to prevent rotation of the first and second adapters relative to each other.

If the threaded connection is between upper and lower motors, a plurality of first adapter electrical terminals are mounted in the first adapter and spaced circumferentially about the axis at a lesser radial distance from the axis than the lugs. A plurality of second adapter electrical terminals in the second adapter are spaced circumferentially about the axis at a lesser radial distance from the axis than the slots, for engagement by the first adapter electrical connectors.

A motor-to-motor connection may have at least one inclined cam surface on each the lugs extends between opposite sides edges of each of the lugs. The cam surfaces engage the side edges of the slots as the first and second adapters are brought together to incrementally rotate one of the adapters relative to the other until the electrical terminals of the first adapter and the second adapter are axially aligned. The lugs protrude axially past the electrical terminals in the first adapter.

A first drive shaft in one of the modules has a splined end. A second drive shaft in an adjoining one of the modules has a splined end. A sleeve coupling has a cylindrical body with an inner wall and an outer wall and internal splines separated by spline grooves in the inner wall. The internal splines slide over and engage the splined end of the second drive shaft. The sleeve has a rim on a first end. Teeth are formed on the rim of the coupling. Each of the teeth extends from the inner wall to the outer wall and is aligned with one of the spline grooves. The teeth incrementally rotate the shafts relative to each other and guide the splined end of the first drive shaft into engagement with the internal splines.

The first adapter has a cylindrical inner wall and a cylindrical outer wall that are concentric with each other. Circumferentially extending recesses are located in the outer wall of the first adapter between adjacent one of the lugs. Each of the recesses has a radial depth that is less than a radial thickness of the first adapter measured the inner and the outer walls of the first adapter. Each of the recesses has a radially outward facing back wall.

Each of the lugs has an inner side and an outer side that cylindrical segments. Each of the lugs has an end that is located in a plane perpendicular to the axis. Each of the lugs may have on an end two cam surfaces that incline from opposite side edges of each of the lugs to a crest. Each of the slots may have a slot base having two inclined surfaces that incline from opposite sides edges of each of the slots to a valley, defining a mating contour for receiving one of the lugs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cropped side view of an electrical submersible pump assembly in accordance with this disclosure.

FIG. 2 is a cross-sectional view of the threaded connection between the seal section and the pump intake of the pump assembly of FIG. 1.

FIG. 3 is an exploded perspective view of the threaded connection of FIG. 2.

FIG. 4 is an exploded perspective view of one embodiment of a threaded connection between the tandem motors of FIG. 1.

FIG. 5 is a perspective view of the head of the lower tandem motor of FIG. 4.

FIG. 6 is a perspective view of a second embodiment of a threaded connection of the lower tandem motor of FIG. 1.

FIG. 7 is a perspective view of the second embodiment threaded connection of the upper tandem motor of FIG. 1.

FIG. 8 is a sectional view of the second embodiment threaded connection between the tandem motors of FIG. 1 in made-up engagement.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring to FIG. 1, electrical submersible pump (ESP) 11 is employed to pump well fluid, typically a mixture of oil and water. ESP 11 may be installed in a vertical portion or a horizontal or inclined portion of a well. The terms “upper”, “lower” and the like are used only for convenience and not in a limiting manner.

ESP 11 has a number of modules, including a pump 13 that may be a centrifugal pump having a large number of stages, each stage having an impeller and a diffuser (not shown). Alternately, pump 13 may be another type, such as a progressing cavity pump. Pump 13 has an intake 15 for drawing in well fluid. A pressure equalizer or seal section 17 connects to the lower end of intake 15 in this example. At least one electrical motor 19 connects to the lower end of seal section 17. In this embodiment, two motors 19, 21 are connected in tandem to each other. Seal section 17 may be conventional and has components for reducing a pressure difference between lubricant in motors 19, 21 and the hydrostatic pressure of the well fluid. ESP 11 could have other modules, such as a gas separator.

The various modules, including pump 13, seal section 17, and tandem motors 19, 21 are typically brought separately to a well site and connected together by connections 23 a, 23 b and 23 c. In this example, each connection 23 a, 23 b and 23 c comprises a threaded collar connection. However, some of the connections between modules, such as the one between tandem motors 19, 21, could be bolted types. FIG. 2 illustrates threaded connection 23 a between seal section 17 and pump intake 15.

Referring to FIG. 2, in this example, an intake adapter 25 extends downward from intake 15 (FIG. 1) concentric with a longitudinal axis 26 of ESP 11. Intake adapter 25 may be an integral portion of pump intake 15 or secured by threads (not shown). Intake adapter 25 has a cylindrical neck 27 with a cylindrical male portion or stab 29 on its lower end. A shoulder ring 31 mounts within an external groove 33 on neck 27. Shoulder ring 31 preferably comprises two semi-circular segments; in this example, the segments are retained in groove 33 with a resilient retainer ring 35 that encircles the outer diameter of shoulder ring 31. Neck 27 carries a collar 37 that is rotatable and axially movable relative to neck 27 until the connection is made up. Collar 37 has an internal shoulder 39 that abuts an upper side of shoulder ring 31 when connection 23 a is made up. Collar 37 has internal threads 41. A seal 43 seals between an outer diameter portion of neck 27 and collar 37.

Male portion 29 has a cylindrical inner wall 44 and a cylindrical outer wall 46 that are concentric with axis 26. Male portion 29 has a rim 48 on its lower end that is in a plane perpendicular to axis 26.

A seal section head or adapter 45 extends upward from seal section 17 (FIG. 1) and may have lower threads (not shown) that secure to internal threads in the housing of seal section 17. Connection 23 a could be inverted, with seal section adapter 45 having neck 27 that carries collar 37 instead of intake adapter 25. A drive shaft (not shown in FIG. 2) extends through seal section adapter 45 and has an upper end that mates with a shaft (not shown in FIG. 2) in intake adapter 25 via an internally splined coupling.

Seal section adapter 45 has a cylindrical receptacle portion 47 into which intake adapter male portion 29 stabs. Seal section adapter 45 has external threads 49 on receptacle portion 47. Internal threads 41 of collar 37 engage external threads 49 during make up. Seals 51 on the exterior of receptacle portion 47 seal against the inner diameter of collar 37 below internal threads 41.

Seal section adapter 45 has an inner cylindrical counterbore wall 52 and an outer cylindrical wall 53 that are concentric with axis 26. Seal section adapter 45 has a shoulder 56 at the base of counterbore wall 52. Male portion rim 48 is spaced a short distance from shoulder 56 when connection 23 is made up.

Referring also to FIG. 3, male portion 29 has a plurality of male portion lugs 55 spaced circumferentially around it and formed in male portion outer wall 46. The outer surfaces of male portion lugs 55 are curved and form part of outer wall 46 for male portion 29. Male portion lugs 55 are preferably identical in circumferential extent and are evenly spaced apart from each other. A recess or male portion slot 57 separates each male portion lug 55 from adjacent lugs. The side edges 55 a of male portion lugs 55 are straight and parallel with axis 26.

In the example of FIG. 3, each male portion slot 57 has an outward-facing curved wall 58 extending between lug side edges 55 a, thus slot 57 does not extend completely through male portion 29 from outer wall 46 to inner wall 44. The radial depth of each slot 57 is less than the radial thickness of male portion 29 between inner wall 44 and outer wall 46. The radial depth of each male portion slot 57 is the same as the radial dimension of each male portion lug side edge 55 a. In the example shown in FIG. 3, the radial dimension of each lug side edge 55 a and each slot 57 is about half or less than the radial thickness of male portion 29 between inner wall 44 and outer wall 46.

An upper end or base 54 of each male portion slot 57 defines a downward facing shoulder. The upper ends 54 of slots 57 in this embodiment are located in a plane perpendicular to axis 26. Male portion rim 48 defines the lower end of each male portion lug 55, thus the lower ends of lugs 55 are also in a plane perpendicular to axis 26. The lower ends of male portion lugs 55 are flush with the circular rim 48 of male portion 29.

Receptacle portion 47 has receptacle portion lugs 59 formed within that mate with intake adapter slots 57. Receptacle portion lugs 59 are formed in receptacle portion inner cylindrical wall 52 and are separated from each other by receptacle portion slots 61. The curved inner surfaces of receptacle portion lugs 59 define the inner diameter of receptacle portion inner cylindrical wall 52. Receptacle portion lugs 59 have straight side edges 59 a that are parallel with axis 26. Receptacle portion slots 61 have inward facing curved surfaces 60 extending between lug side edges 59 a. Receptacle portion slots 61 have radial depths that are the same as the radial dimensions of receptacle portion lug side edges 59 a and substantially the same as the radial dimensions of male portion lug side edges 55 a. The radial dimension of each lug side edge 59 a is less than the radial dimension between inner wall 52 and outer wall 53.

Receptacle portion slots 61 have substantially the same circumferential width and may be slightly greater in axial length than male portion lugs 55. The upper ends 62 of receptacle portion lugs 59 define upward-facing shoulders that are abutted by downward-facing shoulders 54 of male portion slots 57, as shown in FIG. 2. Upper ends 62 are spaced a short distance below the rim of receptacle portion 47 and are located in a plane perpendicular to axis 26. When connection 23 a is made up, shoulders 54 and ends 62 will be in abutting contact, transferring axial forces; however, the lower ends of intake adapter lugs 55 which are located at rim 48, will not be in abutting contact with the lower ends of receptacle portion slots 57.

FIG. 2 is taken along a section line passing through one of the male portion lugs 55 on the left and one of the receptacle portion lugs 59 on the right. When the connection is made up, the curved outer surfaces of male portion lugs 55 will be in contact with receptacle portion curved surfaces or back walls 60 of receptacle portion slot 61 s. Curved surfaces 58 of male portion slots 57 will be in contact with the inner surfaces of receptacle portion lugs 59, which define receptacle portion inner diameter or inner wall 52.

To connect connector 23 a, a technician will move collar 37 upward to a released position on neck 27. The technician aligns intake adapter lugs 55 with seal section adapter slots 61, then stabs male portion 29 into receptacle 47. At the same time, the splines of one of the shafts (not shown) is aligned with splines in the shaft coupling of the other of the shafts. The technician brings collar 37 downward, engages threads 41 with threads 49, and tightens collar 37. Collar shoulder 37 bears against shoulder ring 31, and when made up, seal section adapter slot upper ends 54 bear against intake adapter lug upper ends 62. Male portion lug side edges 55 a will be in contact with receptacle portion lug side edges 59 a. The meshing engagement of intake adapter lugs 55 with seal section adapter slots 61 and the meshing engagement of seal section adapter lugs 59 with intake adapter slots 57 prevent rotation of intake adapter 25 and seal section adapter 45 relative to each other during operation. Motor and seal section connection 23 b may be constructed in the same manner as connection 23 a.

FIG. 4 illustrates one example of tandem motor connection 23 c. Upper motor 19 has an adapter at its lower end with a cylindrical receptacle portion 64. A plurality of electrical terminals 63 are recessed within receptacle portion 64. Preferably, there are at least three terminals 63, each connected to a conductor wire (not shown) for one of the three phases of upper motor 19. Terminals 63 are spaced 120 degrees apart from each other around axis 26. Each terminal 63 is illustrated as being a pin, but it could alternately comprises a sleeve. Upper motor 19 has a rotatably driven drive shaft 65 located on axis 26. Drive shaft 65 has a lower splined end 67 that extends downward a short distance from receptacle portion 64.

Upper motor receptacle portion 64 has a plurality of internal lugs 69 spaced around axis 26 and formed within the inner surface of receptacle portion 64. Lugs 69 extend circumferentially and are spaced from each other by slots 71 of the same circumferential width. Each slot 71 has a radial depth less than the radial thickness of the wall defined by receptacle portion 64. The radial thickness of each lug 69 is also less than the radial thickness of the wall defined by receptacle portion 64. The lower ends of upper motor lugs 69 are located in a single plane perpendicular to axis 26. The number of upper motor lugs 69 may vary and is illustrated to comprise three. The lower ends of electrical terminals 63 are located above the lower ends of upper motor lugs 69. Each upper motor lug 69 has a straight side edges 69 a that are parallel with axis 26.

In this example, the adapter for lower motor 21 comprises the male portion of the connection, but connection 23 c could be inverted. The head or adapter of lower motor 21 has a collar 75 movably carried on an upward-protruding neck 73. Collar 75 is movable from the lower released position shown to an upper position in threaded engagement with external threads 77 formed on upper motor receptacle portion 64. Lower motor lugs 78 extend upward from neck 73 and are dimensioned for close reception in upper motor slots 71. In this example, slots 80 between lower motor lugs 78 extend completely through the wall that defines neck 73, rather than partially as slots 57 and slots 59 in FIG. 3. The radial thicknesses of lower motor lugs 78 is the same as the radial thicknesses of upper motor slots 71. The upper ends of lower motor lugs 78 are located in a single plane perpendicular to axis 26. The side edges 78 a of lower motor lugs 78 are parallel with axis 26 for sliding engaging the side edges 69 a of upper motor lugs 69 during make-up.

Referring to FIG. 5, lower motor lugs 78 have cam surfaces or bevels 84 on their upper edges. Cam surfaces 84 extend from opposite side edges 78 a and are inclined toward each other. Cam surfaces 84 join the upper ends of lugs 78, which may be flat.

The head or adapter of lower motor 21 has electrical terminals 74 mounted within neck 73 and arranged to mate with upper motor electrical terminals 63. The upper ends of electrical terminals 74 are below the upper ends of lower motor lugs 78. Lower motor 21 has a shaft with a splined end and a splined coupling 76 that mate with upper motor shaft splined end 67 (FIG. 4). The upper end of splined coupling 76 is recessed below the upper ends of lower motor lugs 78. Lugs 69 and 78 are positioned so that when upper motor lugs 69 align with lower motor slots 80 (FIG. 4), upper motor electrical terminals 63 will be aligned with the mating electrical terminals 74 of lower motor 21.

Referring to FIG. 4, when making up connection 23 c, a technician aligns lower motor lugs 78 with upper motor slots 71, which also aligns each electrical terminal 74 (FIG. 5) of lower motor 21 with one of the electrical terminals 63 of upper motor 19. The operator brings motors 19, 21 toward each other, causing lower motor lugs 78 to enter upper motor slots 71, and upper motor lugs 69 to enter lower motor slots 80. Cam surfaces 84 may engage the lower ends of upper motor lugs 69, causing slight relative rotation between upper motor 19 and lower motor 21. When this entry first begins, electrical terminals 63, 74 will not yet be engaging each other. Also, drive shaft splined end 67 will not yet be into engagement with splined coupling 76 (FIG. 5). Continued movement toward each other causes electrical terminals 63, 74 to engage each other and drive shaft splined end 67 to engage splined coupling 76. The technician then moves collar 75 upward and secures it to threads 77. The lower edge of each lower recess 80 will abut the lower end of each upper motor lug 69 when engaged.

FIGS. 6-8 illustrate a second embodiment for a connection between upper and lower tandem motors. Lower motor 79 has a head or adapter with a neck 82 that carries collar 81. Collar 81 abuts a shoulder ring 83 on neck 82 in the same manner as the other embodiments. Electrical terminals 85 are spaced 120 degrees apart from each other. The drive shaft of lower motor 79 has an internally splined coupling 87 at its upper end. Coupling 87 optionally may have sawtooth-shaped teeth 88 on its upper end that face upward and extend between the inner and outer diameters of coupling 87. Each tooth 88 defines a ridge 88 a that axially aligns with one of the internal splines 90 in coupling 87. Ridge 88 a of each tooth 88 extends from the inner diameter to the outer diameter of coupling 87.

Lower motor lugs 89 extend upward and are spaced evenly apart from each other. Lower motor lugs 89 are located radially outward from electrical terminals 85. The curved outer sides of lower motor lugs 89 are segments of a cylinder, defining the outer diameter of neck 82. The curved inner sides of lower motor lugs 89 are segments of a cylinder, defining the inner diameter of neck 82. The side edges of each lower motor lug 89 are parallel with axis 26.

Each lower motor lug 89 has a cam surface 91 on its upper end that in this embodiment, comprises two inclined surfaces that intersect each other at an apex 93. The inclined surfaces of cam surface 91 may be generally flat and at an acute angle relative to longitudinal axis 26. Apex 93 is preferably centered on each lower motor lug 89. Alternatively, the cam surface on the upper end of each lower motor lug 89 could be rounded, with curving inclined surfaces joining a rounded apex. Lower motor cam surface 91 is spaced above electrical terminals 85. Splined coupling 87 is shown extending above cam surfaces 91 for illustration purposes, but normally coupling 87 is also recessed below cam surfaces 91.

Lower motor slots 95 separate adjacent lower motor lugs 89 from each other. Slots 95 preferably are configured the same as lower motor lugs 89. Lower motor slots 95 have side edges parallel with axis 26 and a lower edge 97 that has a valley shape. Lower edge 97 comprises two inclined surfaces that extend downward and join each other an obtuse angle junction. Slots 95 extend through the entire radial width of the wall defining neck 82. Lower motor lugs 89 also have the same radial thickness of the cylindrical wall defining neck 82.

Referring to FIG. 7, upper motor 101 has a lower adapter with a cylindrical receptacle portion 103. Upper motor lugs 105 are machined within receptacle portion 103 and have cam surfaces 107 on their lower ends. Cam surfaces 107 may be identical to cam surfaces 91 (FIG. 6) on lower motor lugs 89, each having a triangular apex 109 on a lower end. Upper motor slots 111 separate upper motor lugs 105 and are contoured to accept lower motor lugs 89 (FIG. 6).

Upper motor 101 has electrical terminals 113 that mate with lower motor electrical terminals 85 (FIG. 6). An upper motor drive shaft 115 extends a short distance downward into upper motor receptacle portion 103. The lower end of upper motor drive shaft 115 has axially extending splines 116 on its outer diameter. When upper motor drive shaft 115 engages coupling 87 (FIG. 6), splines 116 engage teeth 88, which guide them into entry with internal splines 90. Upper motor receptacle portion 103 has external threads 117 that are engaged by internal threads in collar 81 (FIG. 6). The apex 109 of each upper motor lug 105 extends farther downward than electrical terminals 113 and drive shaft 115, but is still recessed from rim 114 of upper motor receptacle portion 103. Upper motor lugs 105 are machined within the inner diameter of the cylindrical wall of receptacle portion 103 and have a lesser radial thickness than the cylindrical wall of receptacle portion 103. Similarly, upper motor slots 111 have less radial depth than the wall defining receptacle portion 103.

FIG. 8 is a sectional view illustrating upper motor 101 secured to lower motor 79. A motor wire 119 of upper motor 101 extends to each upper motor electrical terminal 113. A motor wire 121 of lower motor 79 extends to each lower motor electrical terminal 85. Lower motor 79 has a drive shaft 123 extending upward to splined coupling 87. When fully made up, the lower edge 97 of each lower motor slot 95 (FIG. 6) abuts cam surface 107 of one of the upper motor lugs 105.

The embodiment of FIGS. 6-8 makes up the same manner as the motor connector embodiment of FIG. 4. Cam surfaces 91 and 107 allow some initial rotational misalignment to exist between lower motor lugs 89 and upper motor slots 111 and between upper motor lugs 105 and lower motor slots 95. Cam surfaces 91 and 107 will cause incremental rotation of upper and lower motors 101 and 79 relative toe ach other as the technician stabs lower motor neck 82 into upper motor receptacle portion 103. The rotational movement to axially align electrical terminals 85, 113 will occur before electrical terminals 85 and 113 touch each other.

Similarly, the rotational movement caused by cam surfaces 91 and 107 occurs before upper motor drive shaft 115 engages splined coupling 87 (FIG. 6). The lower ends of upper motor drive shaft splines 116 land on teeth 88. If splines 116 and 90 are slightly misaligned, teeth 88 will cause slight rotation between upper motor drive shaft 115 and lower motor drive shaft 123 to align splines 116 and 90. Ridges 88 a of teeth 88 cause splines 116 to slide into the valley of each tooth 88.

The tandem motor connection of FIGS. 6-8 could be inverted from the manner shown. Also, lugs and mating slots of this tandem motor connection could be employed with bolted connections instead of threaded connections having a rotatable collar.

Although the disclosure has been shown in several of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the disclosure. 

1. An electrical submersible pump assembly, comprising: a plurality of modules including a pump, a motor, and a seal section for reducing a pressure differential between lubricant in the motor and hydrostatic pressure of well fluid; a threaded connection between at least two of the modules, comprising: a first adapter and a second adapter, the first and second adapters having a longitudinal axis; a collar rotatably carried and axially movable on one of the adapters, the collar being in threaded engagement with threads of the other adapter when the threaded connection is made up; first adapter lugs spaced circumferentially apart from each other around the first adapter; second adapter slots spaced circumferentially apart from each other around the second adapter; wherein the lugs slide into the slots while the adapters are brought together; and each of the lugs and each of the slots have side edges that are parallel with the axis, the side edges of the lugs abutting the side edges of the slots to prevent rotation of the first and second adapters relative to each other.
 2. The assembly according to claim 1, further comprising: a plurality of first adapter electrical terminals mounted in the first adapter and spaced circumferentially about the axis at a lesser radial distance from the axis than the lugs; a plurality of second adapter electrical terminals in the second adapter and spaced circumferentially about the axis at a lesser radial distance from the axis than the slots, for engagement by the first adapter electrical connectors.
 3. The assembly according to claim 2, further comprising: at least one inclined cam surface on each the lugs extending between opposite sides edges of each of the lugs; and wherein the cam surfaces engage the side edges of the slots as the first and second adapters are brought together to incrementally rotate one of the adapters relative to the other until the electrical terminals of the first adapter and the second adapter are axially aligned.
 4. The assembly according to claim 2, further comprising: a pair of inclined cam surfaces on each the lugs extending between opposite sides edges of each of the lugs toward each other; wherein the lugs protrude axially past the electrical terminals in the first adapter; and the engagement of the cam surfaces of the lugs with the side edges of the slots causes the first and second adapters to incrementally rotate relative to each other until the electrical terminals of the first adapter and the second adapter are axially aligned.
 5. The assembly according to claim 1, further comprising: a first drive shaft in one of the modules, the first drive shaft having a splined end; a second drive shaft in an adjoining one of the modules, the second drive shaft having a splined end, a sleeve coupling having a cylindrical body with an inner wall and an outer wall and internal splines separated by spline grooves in the inner wall that slide over and engage the splined end of the second drive shaft, the sleeve having a rim on a first end; and teeth formed on the rim of the coupling, each of the teeth extending from the inner wall to the outer wall and being aligned with one of the spline grooves for incrementally rotating the shafts relative toe ach other and guiding the splined end of the first drive shaft into engagement with the internal splines.
 6. The assembly according to claim 1, wherein: the first adapter has a cylindrical inner wall and a cylindrical outer wall that are concentric with each other; circumferentially extending recesses are located in the outer wall of the first adapter between adjacent one of the lugs; and each of the recesses has a radial depth that is less than a radial thickness of the first adapter measured the inner and the outer walls of the first adapter.
 7. The assembly according to claim 1, wherein: the first adapter has a cylindrical inner wall and a cylindrical outer wall that are concentric with each other; circumferentially extending recesses are located in the outer wall of the first adapter between adjacent one of the lugs; and each of the recesses has a radially outward facing back wall.
 8. The assembly according to claim 1, wherein: each of the lugs has an inner side and an outer side that are cylindrical segments.
 9. The assembly according to claim 1, wherein: each of the lugs has an end that is located in a plane perpendicular to the axis.
 10. The assembly according to claim 1, wherein: each of the lugs has on an end two cam surfaces that incline from opposite side edges of each of the lugs to a crest; and each of the slots has a slot base having two inclined surfaces that incline from opposite sides edges of each of the slots to a valley, defining a mating contour for receiving one of the lugs.
 11. An electrical submersible pump assembly, comprising: a plurality of modules including a pump, a motor, and a seal section for reducing a pressure differential between lubricant in the motor and hydrostatic pressure of well fluid; a threaded connection between at least two of the modules, comprising: a first adapter having an axis; a second adapter; a collar rotatably carried and axially movable on one of the adapters, the collar being in threaded engagement with threads of the other adapter when the threaded connection is made up; a male portion extending from one of the adapters, the male portion having cylindrical, concentric inner and outer walls; a receptacle portion in the other adapter, the receptacle portion having cylindrical concentric inner and outer walls; male portion lugs formed in the outer wall of the male portion, the male portion lugs being spaced circumferentially apart from each other by male portion slots, each of the male portion slots having a back wall that faces radially outward; receptacle portion lugs formed in the inner wall of the receptacle portion, each of the receptacle portion lugs being spaced circumferentially apart from each by receptacle portion slots, each of the receptacle portion slots having a back wall that faces radially inward; wherein the male portion lugs slide into the receptacle portion slots and the receptacle portion lugs slide into the male portion slots while the adapters are brought together; and each of the male portion lugs and each of the receptacle portion lugs have side edges that are parallel with the axis, the side edges of the male portion lugs sliding along the side edges of the receptacle portion slots as the male portion lugs slide into the receptacle portion slots, to prevent rotation of the first and second adapters relative to each other.
 12. The assembly according to claim 11, wherein the outer wall of the male portion is in contact with the back walls of the receptacle portion slots when the connection is made up.
 13. The assembly according to claim 11, wherein: each of the male portion slots has a radial depth less than a radial thickness of the male portion measured between the inner and outer walls of the male portion at the male portion lugs.
 14. The assembly according to claim 11, wherein: each of the receptacle portion slots has a radial depth less than a radial thickness of the receptacle portion measured between the inner and outer walls of the receptacle portion at the receptacle portion lugs.
 15. The assembly according to claim 11, wherein: each of the male portion slots has a shoulder extending between the side edges of each of the male portion slots; and each of the receptacle portion lugs has an end that abuts one of the shoulders when the connection is made up.
 16. An electrical submersible pump assembly, comprising: a plurality of modules including a pump, a motor, and a seal section for reducing a pressure differential between lubricant in the motor and hydrostatic pressure of well fluid; a threaded connection between at least two of the modules, comprising: a first adapter having an axis; a second adapter; a collar rotatably carried and axially movable on one of the adapters, the collar being in threaded engagement with threads of the other adapter when the threaded connection is made up; first adapter lugs spaced circumferentially apart from each other around the first adapter; second adapter lugs spaced circumferentially apart from each other around the second adapter that slide between the first adapter lugs while the first and second adapters are brought together; each of the first adapter lugs and the second adapter lugs having side edges that are parallel with the axis, the side edges of the first adapter lugs abutting the side edges of the second adapter lugs to prevent rotation of the first and second adapters relative to each other; a plurality of first adapter electrical terminals mounted in the first adapter and spaced circumferentially about the axis at a lesser radial distance from the axis than the first adapter lugs; a plurality of second adapter electrical terminals in the second adapter and spaced circumferentially about the axis at a lesser radial distance from the axis than the second adapter lugs, for engagement by the second adapter electrical connectors; at least one inclined cam surface on an end of each of the first adapter lugs extending between opposite sides edges of each of the first adapter lugs; at least one inclined cam surface on an end of each of the second adapter lugs extending between opposite side edges of each of the second adapter lugs; and wherein the cam surfaces of the first adapter lugs engage the cam surfaces of the second adapter lugs as the first and second adapters are brought together to incrementally rotate one of the adapters relative to the other until the electrical terminals of the first adapter and the second adapter are axially aligned.
 17. The assembly according to claim 16, wherein: the cam surfaces on each of the lugs intersect each other at a crest equidistant between the side edges of each of the lugs.
 18. The assembly according to claim 16, wherein: the first adapter lugs protrude axially past the electrical terminals in the first adapter; and the second adapter lugs protrude axially past the electrical terminals in the second adapter.
 19. The assembly according to claim 16, further comprising: a first drive shaft in one of the modules, the first drive shaft having a splined end; a second drive shaft in an adjoining one of the modules, the second drive shaft having a splined end, a sleeve coupling having a cylindrical body with an inner wall and an outer wall and internal splines separated by spline grooves in the inner wall that slide over and engage the splined end of the second drive shaft, the sleeve having a rim on a first end; and teeth formed on the rim of the coupling, each of the teeth extending from the inner wall to the outer wall and being aligned with one of the spline grooves for incrementally rotating the shafts relative to each other and guiding the spliend end of the first drive shaft into engagement with the internal splines.
 20. The assembly according to claim 16, wherein: the second adapter lugs define slots between them; and each of the slots has a base with a contour mating with the cam surface on each of the first adapter lugs. 